The discussion below is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.
Aspects of the invention relate to a system for mooring a substantially cylindrical floating production, storage and offloading unit. Commonly used in the offshore hydrocarbon production industry are FPSO (Floating Production, Storage and Offloading) units. These FPSOs are commonly turret-moored.
The turret-mooring allows the FPSO to weathervane (pivot) around the turret into the most favorable heading.
Disconnectable turret-moored FPSOs have been built to allow the FPSO to leave the offshore location, for instance to have repairs or facility upgrades inshore, to get out of the projected route of an iceberg or to go to a sheltered area in case of a hurricane warning.
With an increasing number of production lines (risers) to the FPSO it becomes more and more difficult to design these turret mooring systems. As such permanently moored FPSO units have been designed and built which do not have a need to weathervane, and as such they do not require a turret system. For ship-shape hulls this can only be applied in mild weather areas. Another possibility is to design the FPSO hull as a cylindrical structure. Such shape can be moored in more harsh environments.
Presently, cylindrical shaped FPSO's (such as shown in U.S. Pat. No. 6,945,736) do not have a disconnectable mooring and riser system which allows these units to easily leave their offshore location without the mobilization of an installation spread.